Machines for evacuating electron discharge devices and the like



Jan. 10, 1956 L SPENCER 2,730,280

P. MACHINES FOR EVACUATING ELECTRON DISCHARGE DEVICES AND THE LIKE Filed Nov. 5, 1954 ig 22 i --/5 /NVENTO/? PERCY L. SPENCER A TTO/E'NEV United States Patent MACHINES FOR EVACUATING ELECTRON DISCHARGE DEVICES AND THE LIKE Percy L. Spencer, Waban, Mass., as'signor to Raytheon Manufacturing Company, Waltham, Mass, a corporation of Delaware Application November 5, 1954,- Serial No. 467,183 8 Claims. (Cl. 226-204) This invention relates to the evacuation of a chamber, and more specifically to the evacuation of an electron discharge device wherein the external surfaces of said device are not oxidized from the high temperatures used in the evacuating processes.

This invention discloses a particular system whereby an electron discharge device in the process of being evacuated is enveloped in an atmosphere of carbon dioxide (CO2) gas. In the commercial processes used to evacuate electron discharge devices, such as a magnetron, the magnetron is placed on a movable machine which moves through a complete series of stages that automatically degas, evacuate, and seal the vacuum tube. In previous automatic evacuating procedures, it was practically impossible to surround each magnetron with a protective gas cover because a continuing supply of the gas was needed as the tube moved from stage to stage, thereby necessitating a complicated maze of valves and tubing.

Carbon dioxide gas is used primarily to keep the outside surfaces of the magnetron from being oxidized due to the high temperatures used in the aforementioned process. A secondary advantage of enveloping the magnetron with carbon dioxide gas is that should a leak or other defect occur in the evacuating process, the interior of the magnetron will immediately be filled with the carbon dioxide gas, thereby preventing oxidation of the interior of the magnetron. It can be seen, therefore, that using carbon dioxide gas saves a cleaning operation that would otherwise be necessary for every processed magnetron. A cleaning step is also saved for those tubes that must be processed due to leaks developing in the vacuum seal.

An object of the present invention is to disclose a simplified procedure for enveloping each tube in an automatic evacuating machine, with carbon dioxide (CO2) gas.

Another object of this invention is to accomplish the aforesaid in a practical, cheap and simple manner by using a container of Dry Ice as the source of the carbon dioxide, whereby a separate container travels with each tube as it goes from stage to stage.

Further objects and advantages of this invention will be apparent as the description progresses, reference being made to the accompanying drawing wherein:

Fig. 1 is an embodiment of a completely automatic evacuating machine; and

Fig. 2 is a section of a pumping position illustrating an embodiment of this invention.

Referring now to Figs. 1 and 2, there is shown a rotary system 10 for automatically moving the electron discharge device, such as a magnetron 11, from stage to stage. For the proper evacuation of a magnetron, a three-stage diffusion pump 12 and a mechanical pump 13 are connected to the exhaust tube 14 of the magnetron tube 11 being evacuated. Since both the diifusion pump 12 and the mechanical pump 13 must be connected to the magnetron 11 as it goes from stage to stage, there is supplied a separate diflusion pump 12 and a separate mechanical pump evacuated.

For the proper evacuating and de-gassing of the tube, the magnetron 11 is subjected to an external heating stage 15 for the purpose of removing the rough gas entrapped in the surface molecules of the chamber being evacuated. The second stage of the evacuating process consists of an arrangement for producing internal heat within the magnetron structure. This is accomplished by automatically supplying a voltage to the filament of magnetron 11 in the filament heating stage 16. Depending on the particular tube being evacuated, the filament voltage will be automatically varied over a specific range calculated to heat the cathode to such a point as to drive the gas molecules from the surface of the cathode structure. The third stage consists of an actual operating stage 17. This is accomplished by having stage three automatically apply both the filament and the anode volt- 13 for each magnetron tube 11 being 17 and 13 form no part of the present invention and, since they may be of any presently well-known form, they are not illustrated herein.

As the magnetron tube 11 progresses from stage to stage both dilfusion pump 12 and mechanical pump 13 travelling with the tube maintain the exhaust at all times. Attached to the same moving rotary system 10 that the magnetron tube 11 is attached to for moving from stage to stage is a tank 19 containing solidified carbon monoxide commonly known as'Dry Ice. A tube 20 connected to the top 21 of said tank is brought within close proximity of the magnetron tube 11 being evacuated and it is open to the atmosphere at a point higher than the highest point of said magnetron tube 11. A cover 22 constructed of a material possessing good thermal conductivity and having a pinhole 23 centrally located in said cover is placed over the magnetron tube 11 being evacuated and the exhaust tube 20 from tank 19 and placed on a support plate is to supply a concen- At the very start of the process after the cover 22 is placed in position, a vacuum causing device, such as a pilot flame 24, is placed over the pinhole 23 for the purpose of causing a low pressure in said baking chamber that will cause the CO2 gas from tank 19 to completely envelop said baking chamber.

It can be seen, therefore, that sufficient Dry Ice must be placed in tank 19 depending on the length of time for the magnetron 11 to complete the cycle from stage to stage to the final sealing means. In this manner, mechanical pump 13, diffusion pump 12, magnetron tube 11, tank 19, and cover 22 all move together from stage to stage on the rotary system 10, thereby eliminating the need for complicated valves and tubing.

This completes the description of the embodiment of the invention illustrated herein. However, many modifications, uses, and advantages thereof will be apparent to persons skilled in the art without departing from the spirit and scope of this invention. Accordingly, it is desired that this invention not be limited to the particular details of the embodiment disclosed herein except as defined by the appended claims.

What is claimed is:

l. A machine comprising means for supporting a plurality of electron discharge devices, means for moving said supporting means through a station at which heating means is located, a plurality of containers containing carbon dioxide, one for each electron discharge device mounted on said moving means, and means for enveloping said electron discharge devices with carbon dioxide gas evolved from said containers.

2. A machine comprising means for supporting a plurality of electron discharge devices, means for moving said supporting means through a station at which evacuation means is located for exhausting said electron discharge devices, a plurality of containers containing carbon dioxide, one for each electron discharge device mounted on said moving means, and means for enveloping said electron discharge devices with carbon dioxide gas evolved from said containers.

3. A machine comprising means for supporting a plurality of electron discharge devices, means for moving said supporting means through a station at which heating means and evacuation means are located, a plurality of containers containing carbon dioxide, one for each elec tron discharge device mounted on said moving means, and means for enveloping said electron discharge devices with carbon dioxide gas evolved from said containers.

4. A machine comprising means for supporting a plurality of electron discharge devices, means for moving said supporting means through a station at which heating means is located, a plurality of containers containing carbon dioxide, one for each electron discharge device mounted on said moving means, a separate cover constructed of a material having good thermal conductivity mounted on said supporting means for covering each electron discharge device, and means for enveloping the internal area of said cover with carbon dioxide gas from said container.

5. A machine comprising means for supporting a plurality of electron discharge devices, means for moving said supporting means through a station at which heating means is located, a plurality of containers containing carbon dioxide, one for each electron discharge device mounted on said moving means, a separate cover constructed of a material having good thermal conductivity mounted on said supporting means for covering each electron discharge device, and a pipe leading from said container containing the carbon dioxide to a point in said cover for enveloping said electron discharge device with carbon dioxide gas.

6. A machine comprising means for supporting a plurality of electron discharge devices, means for moving said supporting means through a station at which heating means is located, a plurality of containers of Dry Ice, one for each electron discharge device mounted on separate supporting means, a separate cover constructed of a material having good thermal conductivity mounted on said supporting means for covering each electron discharge device, and means for enveloping said electron discharge devices with carbon dioxide gas evolved from said containers.

7. A machine comprising means for supporting a plurality of electron discharge devices, means for moving said supporting means through a station at which heating means is located, a plurality of containers of Dry Ice, one for each electron discharge device mounted on said supporting means, a separate cover constructed of a material having good thermal conductivity mounted on said supporting means for covering each electron discharge device, and a pipe leading from said container containing the carbon dioxide to a point in said cover for enveloping said electron discharge device with carbon dioxide gas.

8. A machine comprising means for supporting a plurality of electron discharge devices, means for moving said supporting means through a station at which heating means is located, a plurality of containers of Dry Ice, one for each electron discharge device, mounted on separate supporting means, a separate cover constructed of a material having good thermal conductivity mounted on said supporting means for covering each electron discharge device, said cover having a hole located in its uppermost portion, a pipe leading from said container containing the carbon dioxide to a point in said cover for enveloping said electron discharge device with carbon dioxide gas, and means for supplying a vacuum to the hole located in said cover for accelerating the process of filling the internal portion of said cover with carbon dioxide gas.

References Cited in the file of this patent UNITED STATES PATENTS 

